As known, keyboards and mouse devices are indispensable devices for people in the modern society to operate computers. Generally, each of the keyboard and the mouse has plural keys on the top surface. The user may press the keys to input commands. Conventionally, in the keyboard and the mouse, many kinds of keys are designed to generate key signals. For example, a mechanical key uses conductive pins to trigger a multi-stage switch to generate a key signal. In addition, an optical key generates a key signal according to the result of receiving or obstructing a sensing light.
However, the above key designs still have some drawbacks. For example, the force level of a resisting force to resist the pressing action of the key and the predetermined force level for triggering the key are set before the keyboard or the mouse leaves the factory. That is, the force level cannot be adjusted by the user. Consequently, the conventional keyboard and the conventional mouse cannot meet the requirements of different users (e.g., children and adults). For example, it is laborious for the children to press the key, but the feedback force level is insufficient to the adult. In other words, the conventional input device needs to be further improved.